The present invention relates to a method for changing the clutch torque of a clutch in the power train of a vehicle having an automated manual shift transmission and/or an automated clutch in a creep drive mode of the vehicle. The present invention also relates to a method for changing the clutch torque of a clutch in the power train of a vehicle having an automated manual shift transmission and/or an automated clutch to establish the biting point of the clutch.
When a vehicle having an automated manual shift transmission and/or an automated clutch is moved in a creep drive mode to park in a parking space, for example, it must be ensured that the drive motor is not brought to stop by the driver of the vehicle during a braking procedure. For this purpose, opening the clutch when the driver actuates the brake of the vehicle is already known, it being possible to monitor the brake light switch in order to monitor the braking procedure. Therefore, digital information exists on whether the brake is actuated and the clutch must therefore be opened in order to avoid the engine dying because of the braking torque exerted on the engine.
However, when the driver only wishes to brake a little against a creep torque transmitted by the clutch during maneuvering, this procedure corresponds to a different driver intent than the sharp braking by the driver in order to avoid a collision during the parking procedure, for example.
By monitoring the engine speed, it is possible to activate more rapid opening of the clutch if the instantaneous engine speed falls below the engine-specific idle speed for a predetermined period of time. However, if a diesel engine is used as the drive motor, it reacts significantly more rapidly than a gasoline engine to a reduction in the engine speed, through an increase in the engine torque output because of the combustion, so that a noticeable drop in the engine speed may not be perceived, but rather the driver of the vehicle would perceive a push of the engine against his braking intent.
For the adaptation of the touch point or biting point of the clutch, exploiting the reaction of the engine in the event of an activation of the clutch using touch ramps when the brake is actuated is known. For this purpose, a low clutch torque is built up with an initially open clutch and the torque output by the engine is monitored. If the engine torque increases by a specific value over a specific period of time in relation to the engine torque before the touch point adaptation, then the biting point established by the clutch controller must be corrected in the open direction. For such a procedure, it is possible that the vehicle will roll free if the brake is only lightly actuated.